This invention relates to flexible shaft couplings, and more particularly to flexible couplings of the type in which coupling hub members affixed to adjacent ends of the shafts to be coupled are each provided with axially directed peripheral teeth which define grooves adapted to receive resilient interconnecting grid members.
The shaft couplings in which a grid interconnects with teeth of hubs disposed on adjacent ends of driving and driven shafts, with the grid functioning as the resilient torque transmitting element between the shafts, have found wide use since first proposed in U.S. Pat. No. 1,391,713 issued Sept. 27, 1921 to J. Bibby. Such couplings are able to accommodate parallel and angular misalignments of the coupled shafts and also permit axial end float of the shafts by reason of the ability of the grid to slide in the grooves between the teeth. The side walls of the teeth are normally crowned, as in the Bibby patent, so that the unsupported length of the rungs of the grid which span the space between the hubs will decrease as the torsional load increases. This torsional flexibility permits the coupling to absorb impact energies thus dampening vibration and reducing peak or shock loads.
In the Bibby U.S. Pat. No. 1,391,713 the grid was formed of a stout wire bent to and fro and the grooves between the teeth of the hub members were formed with a square bottom and parallel sides. Subsequent forms of the basic type of coupling have used grids with rectangular cross sections also in grooves having square bottoms, as exemplified by U.S. Pat. No. 2,969,658 of E. J. Wellauer, issued Jan. 31, 1961, and grids with a generally trapazoidal cross section with mating tapered grooves, as illustrated in U.S. Pat. No. 3,079,773 of W. P. Schmitter, issued Mar. 5, 1963. Bent wires have also been employed to form interconnecting spring elements in a different form of flexible coupling illustrated in German Pat. No. 735,393 issued May 13, 1943 to Albert Tacke.
It is a principal object of this invention to provide a flexible coupling of the type using an interconnecting grid which will exhibit improved fatigue life as compared with the forms of couplings heretofore known. The improved fatigue life is achieved by providing a coupling in which the grooves defined between the teeth of the hubs have a rounded bottom, and in which the interconnecting grid has rungs of a circular cross section which are seated in the grooves.
It is another object of this invention to provide a flexible coupling which employs to maximum advantage the greater flexibility inherent in an interconnecting grid having rungs of circular cross section. The greater flexibility is employed to achieve excellent operating characteristics and also to permit ease of assembly. The ease of assembly is enhanced by providing the grooves with side walls which diverge outwardly from the axis of rotation of the hubs. The ease of assembly is particularly important when more than a single layer of rungs are disposed in each groove. Multiple layers of grids will reduce the stiffness of the coupling compared to a single grid with the same torque transmitting capacity.